DISCUSSION OF THE PRIOR ART
Many attempts have been made to develop large-screen displays for use in television receivers or the like. A variety of different techniques have been employed heretofore, each with its unique problems. Projection TV systems employing three separate, high-intensity CRTs, one each for red, blue and green, in conjunction with a projection lens system have been popular. These systems have suffered from high cost and low light intensity which has required special projection screens and viewing under very low ambient light conditions. In addition, the need to converge three separate CRT images has often resulted in a poorly converged, fuzzy screen image. CRT life has also been limited because the extremely high intensities required for image projection require high beam currents.
Another method for providing a large-screen display has been to use a conventional, single-CRT television receiver and by means of mirror and/or lens systems, to rear-screen project an enlarged image onto a screen forming a part of the television receiver cabinet. While this type of system has overcome the convergence problems inherent in the three-CRT projection systems, they are not without their problems. Image intensity is still relatively low and the costs have heretofore been high. Large cabinets are generally required to house the CRT and the required lens/mirror system.
Flat panel displays including tiled flat panel displays are now entering the marketplace and promise to provide an excellent choice for large-screen displays in the future. At this time, flat-panel displays are still prohibitively expensive for all but the highest end applications.
U.S. Pat. No. 3,043,910, for FIBER OPTICAL IMAGE TRANSFER DEVICE; issued Jul. 10, 1962 to J. W. Hicks, Jr. teaches the use of a plurality of optical fibers for the transfer of an image from a relatively small cathode ray tube (CRT) to a much larger viewing surface. Hicks also teaches methods of manufacturing fiber optical devices for performing the image transfer and enlargement functions. In contradistinction, the fiber optic display screen of the present invention utilizes the unique fiber optical coupling device, the subject of my above-identified copending patent application. This unique coupling device provides greater uniformity of intensity over the viewing area than is possible with the Hicks or similar systems.
The use of fiber optic device attached to or forming a part of a CRT is known. U.S. Pat. No. 3,826,944 for CATHODE RAY TUBE WITH INORGANIC PHOSPHOR AND FIBER FACEPLATE; issued Jul. 30, 1974 to Kenneth Cooper teaches such a system. The Cooper device utilizes an essentially conventional CRT having a phosphor which radiates in the ultraviolet (UV) spectrum on the inner surface of a fiber optic window. On the outer surface of the fiber optic window is placed a UV-transmissive, visible-absorbing filter layer. An organic phosphor emitting light in the visible range upon excitation by UV energy is disposed on the filter layer. Finally, a visible light transmitting, UV-blocking filter is disposed over the phosphor layer. This arrangement results in a high-contrast CRT which produces an image suitable for viewing in high ambient light conditions. The particular construction causes ambient light striking the CRT face to be absorbed without degrading the image. The system of the present invention does not use a fiber optic array as part of a face plate. In addition, relatively long fibers are extended from the face plate of a CRT to a remote viewing screen region. Finally, the inventive system does not rely on UV energy-excited phosphor for the production of visible light.
U.S. Pat. No. 4,739,172 for FIBER OPTIC PHOSPHOR SCREEN AND A METHOD OF MANUFACTURING THE SAME; issued Apr. 19, 1988 to Yoshiharu Obata, et al. teaches the coating of a light-emitting phosphor on one side of a fiber optic plate. The plate consists of a large number of bundled, single, clad optical fibers. A depression in the end of the fiber facing the phosphor layer of the screen is removed to leave a depression which prevents a direct contact between the core region of the optical fiber and the phosphor. The Yoshiharu, et al. apparatus is designed for inclusion within an evacuated envelope of an X-ray intensifier. Consequently, the optical fibers employed are a few millimeters in length. The phosphor used on the Yoshiharu, et al. System is also designed to emit visible light when excited by electromagnetic energy in the X-ray band. In contradistinction, the system of the present invention may be external to a CRT, X-ray image enhancer, or the like. The optical fibers used in the invention may be several meters in length. Also, the phosphor is designed to be excited by electromagnetic energy in the X-ray band having a wavelength of between 300 nanometer (nM) and 800 nM. In the preferred embodiment the chosen prosper is an inorganic, non-crystalline cathodoluminescent material doped with impurities ranging from 1 part in 100,000 to 1 part in 100 to produce red, green, or blue visible light emission.
Another use of fiber optics in conjunction with a CRT face plat is taught in U.S. Pat. No. 5,127,080 for PSEUDO-INTAGILIATED FIBER OPTIC PHOSPHOR SCREEN AND METHOD; issued Jun. 30, 1992 to Daniel D. Duggan, Sr. The Duggan system provides both a high-resolution image and high light output by using phosphor islands bonded to the ends of individual optical fibers of a fiber optic array. Again, unlike the system of the present invention, the optical fibers employed are a few millimeters in length. The Duggan system does not teach the enlargement of the image through the use of the unique optical coupler used in the system of the instant invention.
U.S. Pat. No. 5,453,879 for REAR PROJECTION SCREEN WITH HIGH OFF-AXIS SUNLIGHT REJECTION; issued Aug. 6, 1996 to Randall D. Blanchard teaches the use of an array of optical fibers as a face plate in a rear-screen image projection apparatus. The use of the optical fiber array provides a high degree of blocking of any incident light impinging of the front surface of the projection screen. There is no use of the unique optical coupler employed as in the system of the present invention. The optical fiber array is also thin relative to the length of the optical fiber array of the present invention, and serves an entirely different purpose.
It is therefore an object of the present invention to provide a fiber optic display screen separable from a CRT thus allowing versatility in placing the CRT relative to the display screen.
It is another object of the invention to enlarge the image from the CRT screen.
It is yet another object of the invention to fabricate the inventive optical display screen to utilize the unique optical coupling devices as described in my above-identified, co-pending patent application.
It is a further object of the invention to provide a simple and inexpensive method for assembling the optical display screen of the present invention.